JPA框架实现分页查询和条件查询功能详解

public interface WinesWorldnetCultureRepository extends JpaRepository<WinesWorldnetCulture,Long>, 
						JpaSpecificationExecutor<WinesWorldnetCulture> {
}

@Service
public class WinesWorldnetCultureService {
    @Autowired
    private WinesWorldnetCultureRepository repository;
    public static Integer total = null;
    public List<WinesWorldnetCulture> getPageData(Integer pageNum, Integer pageSize, String title){
        // 构造条件查询，根据名称查询
        Specification<WinesWorldnetCulture> spec = new Specification() {
            @Override
            public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder builder) {
                return query.where(builder.equal(root.get("title"),title)).getRestriction();
            }
        };
        List<WinesWorldnetCulture> winesWorldnetCultureList = null;
        if (Objects.isNull(pageNum)|| Objects.isNull(pageSize)){
            // 判断分页查询条件是否为空，若为空，则查询所有数据，否则，根据条件进行查询
            return StrUtil.isBlank(title)? repository.findAll(): repository.findAll(spec);
        }
        // 如果页数小于1，则设置页数为1
        if (pageNum<1){
            pageNum=1;
        }
        // 起始页为第 0 页，进行条件分页查询操作
        // 构建分页查询
        PageRequest pageRequest = PageRequest.of(pageNum-1,pageSize);
        Page<WinesWorldnetCulture> winesWorldnetCulturePage = null;
        if (StrUtil.isBlank(title)){
         	// 分页查询操作
            winesWorldnetCulturePage = repository.findAll(pageRequest);
        }else {
        	// 分页加条件查询
            winesWorldnetCulturePage = repository.findAll(spec, pageRequest);
        }
        winesWorldnetCultureList = winesWorldnetCulturePage.getContent();
        total = winesWorldnetCulturePage.getTotalPages();
        return winesWorldnetCultureList;
    }
}

// 构造条件查询，根据名称查询
Specification<WinesWorldnetCulture> spec = new Specification() {
    @Override
    public Predicate toPredicate(Root root, CriteriaQuery query, CriteriaBuilder builder) {
    	// 支持链式编程
        return query.where(builder.equal(root.get("title"),title)).getRestriction();
    }

// 分页查询页数默认是第0页开始
PageRequest pageRequest = PageRequest.of(pageNum-1,pageSize);